1. Field of the Invention
Embodiments of the invention generally relate to an electrode device for a medical implant and to a medical device having an electrode device.
2. Description of the Related Art
Medical implants, such as implantable defibrillators, cardiac pacemakers, etc., stimulate heart muscle with the aid of electrical pulses, which are guided from a battery-operated unit via an electrode to the heart.
Individuals fitted with a cardiac pacemaker, under the action of strong static and alternating magnetic fields of more than one tesla, as are used for example in diagnostic devices such as magnetic resonance tomographs, are typically subject to severe limitations in order to avoid endangerment caused by interaction between the magnetic fields and components of the cardiac pacemaker. Cardiac pacemakers and implantable defibrillators, etc. can be damaged by the strong magnetic fields or may injure the patient as a result of interactions with the magnetic fields. Contact areas of implanted electrodes may heat up, magnetic parts of the implant could move in the magnetic field, or an interference with the function of the electric control of the implant may occur. Those individuals fitted with a cardiac pacemaker should therefore only be subject to examination in a magnetic resonance tomograph under specific conditions, if at all.
In magnetic resonance tomographs, by superimposing a static magnetic field B0 with a magnetic alternating field, a precession movement of a nuclear spin of water molecules is excited in the body of the patient. The precession movement occurring with Larmor frequency. The Larmor frequency is dependent on the strength of the static magnetic field B0 and on the particles in question, for example protons, and is 42.58 MHz for protons at one tesla. The high-frequency additional field, which is oriented transverse to the static magnetic field and of which the frequency is in resonance with the Larmor frequency, deflects all nuclei in a phase-synchronous manner from their current position to the static field Bo. Signals upon relaxation of the nuclei, or of the nuclear spin, can be detected and used for highly accurate imaging of the tissue. The Larmor frequency lies in the VHF range and interferes with the electronic components of medical implants.